Alzheimer's disease (AD) is a progressive degenerative disease of the brain primarily associated with aging. Prevalence of AD in the United States in 2000 was close to 4.5 Million. It was estimated that about one in ten individuals over 65 and nearly half of those over 85 are affected by Alzheimer's disease. Approximately 360,000 patients will be diagnosed with AD each year in the United States alone.
Clinical presentation of AD is characterized by loss of memory, cognition, reasoning, judgment, and orientation. As the disease progresses, motor, sensory, and linguistic abilities are also affected until there is global impairment of multiple cognitive functions. These cognitive losses occur gradually, but typically lead to severe impairment and eventual death in the range of four to twelve years.
Alzheimer's disease is characterized by two major pathologic observations in the brain: neurofibrillary tangles and beta amyloid (or neuritic) plaques, comprised predominantly of an aggregate of a peptide fragment know as beta amyloid peptide Aβ. Individuals with AD exhibit characteristic beta-amyloid deposits in the brain (beta amyloid plaques) and in cerebral blood vessels (beta amyloid angiopathy) as well as neurofibrillary tangles. Neurofibrillary tangles occur not only in Alzheimer's disease but also in other dementia-inducing disorders.